Composite hat stiffener, composite hat-stiffened pressure webs, and methods of making the same

ABSTRACT

There is provided a method of making a composite hat stiffener. The method has the steps of curing a composite hat stiffener in a hat tool to form a pre-cured composite hat stiffener. The pre-cured composite hat stiffener has a composite hat section, a plurality of composite stiffening plies with a body ply, a wrap ply, and a base ply, all coupled to the composite hat section, wherein the body ply is coupled to a first side of the composite hat section, the wrap ply is coupled to the body ply, and the base ply is coupled to the body ply and the wrap ply, a pair of radius filler noodles coupled to the composite hat section and disposed between the plurality of composite stiffening plies, and an outer ply coupled to the composite hat section. The method further includes bonding the pre-cured composite hat stiffener to a structure surface.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of and claims priority topending application Ser. No. 13/531,583, filed Jun. 24, 2012, andentitled COMPOSITE HAT STIFFENER, COMPOSITE HAT-STIFFENED PRESSURE WEBS,AND METHODS OF MAKING THE SAME, the entire contents of which isincorporated herein by reference.

BACKGROUND

1) Field of the Disclosure

The disclosure relates generally to composite reinforcing supportstructures, and more specifically, to composite hat stiffenerconfigurations and methods used in forming composite hat-stiffenedpressure webs, such as for use in aircraft.

2) Description of Related Art

Composite structures are used in a wide variety of applications. Inaircraft construction, composites are used in increasing quantities toform the fuselage, wings, tail section and other components. Forexample, aircraft fuselage structures, such as bulkheads and pressuredecks, may be formed of composite stiffened panel structures comprisingcomposite pressure web or skin panels to which reinforcing stiffenersmay be attached or bonded to improve the strength, stiffness, bucklingresistance, and stability of the composite pressure web or skin panels.The reinforcing stiffeners attached or bonded to the composite pressureweb or skin panels may be configured to carry various loads.

Known reinforcing stiffeners used with such composite pressure web orskin panels may include I-beam stiffeners (a beam with an I-shapedcross-section). However, known I-beam stiffened composite panelsreinforced with such known I-beam stiffeners may experience highpull-off loads at the radius filler, i.e., “noodle”, portions of theI-beam stiffener or at the radius common to the attached flange of thereinforcing stiffener in the region of the noodle. As used herein,“pull-off load” means a shear load and/or moment force applied to acomposite component part, such as a reinforcing stiffener, at locationswhere the composite component part is attached or bonded to a structure,such as a composite pressure web or skin panel, such that the shear loadand/or moment force may cause delamination or separation of thereinforcing stiffener from the attached structure. As used herein,“radius filler noodle” means a composite material or adhesive/epoxymaterial having a triangular cross-section that is used to fill a gapleft by the radius of curved pieces of a composite component part, suchas a reinforcing stiffener.

To decrease the likelihood of delamination or separation of the I-beamstiffener from the composite pressure web or skin panel due to highpull-off loads, numerous additional radius filler elements, fasteners,and/or angle fittings may be required at the locations or joints wherethe I-beam stiffener is attached or bonded to the composite pressure webor skin panel. Such radius filler elements, fasteners, and/or anglefittings may provide additional structural reinforcement to thelocations or joints and distribute the shear load and/or moment force inorder to reduce the risk of delamination at the radius filler or noodleportions of the I-beam stiffener.

However, the use of such numerous additional radius filler elements,fasteners, and/or angle fittings may result in increased productiontime, increased part count and expense, increased labor andmanufacturing costs to install and maintain the parts, and an overallincrease in the complexity of the structure. Moreover, the use offasteners or angle fittings that require mechanical fastening to thereinforcing stiffener or composite pressure web or skin panel mayrequire the formation of appropriately-sized holes in the compositematerial or structure. This, in turn, may require the use of specializedtooling to form such holes in the composite material or structures. Suchspecialized tooling may result in further increased labor andmanufacturing costs.

Accordingly, there is a need in the art for an improved compositestiffener and improved composite stiffened structures and methods ofmaking the same that provide advantages over known configurations,structures and methods.

SUMMARY

This need for an improved composite stiffener and improved compositestiffened structures and methods of making the same is satisfied. Asdiscussed in the below detailed description, embodiments of an improvedcomposite hat stiffener and an improved composite hat-stiffenedstructure and method of making the same may provide significantadvantages over known configurations, structures and methods.

In an embodiment of the disclosure, there is provided a composite hatstiffener. The composite hat stiffener comprises a composite hat sectionhaving a first side and a second side. The composite hat stiffenerfurther comprises a plurality of composite stiffening plies coupled tothe composite hat section. The plurality of composite stiffening pliescomprises a body ply coupled to the first side of the composite hatsection, a wrap ply coupled to the body ply, and a base ply coupled tothe body ply and the wrap ply. The composite hat stiffener furthercomprises a pair of radius filler noodles coupled to the composite hatsection and disposed between the plurality of composite stiffeningplies. The composite hat stiffener further comprises an outer plycoupled to the second side of the composite hat section.

In another embodiment of the disclosure, there is provided a compositehat-stiffened pressure web. The composite hat-stiffened pressure webcomprises an uncured composite pressure web. The composite hat-stiffenedpressure web further comprises a composite hat stiffener bonded to theuncured composite pressure web. The composite hat stiffener is pre-curedand comprises a composite hat section having a first side and a secondside. The composite hat stiffener further comprises a plurality ofcomposite stiffening plies coupled to the composite hat section. Theplurality of composite stiffening plies comprises a body ply coupled tothe first side of the composite hat section, a wrap ply coupled to thebody ply, and a base ply coupled to the body ply and the wrap ply. Thecomposite hat stiffener further comprises a pair of radius fillernoodles coupled to the composite hat section and disposed between theplurality of composite stiffening plies. The composite hat stiffenerfurther comprises an outer ply coupled to the second side of thecomposite hat section.

In another embodiment of the disclosure, there is provided a method ofmaking a composite hat-stiffened pressure web to reduce effects ofpull-off load and to improve stability of a pressure web. The methodcomprises curing a composite hat stiffener in a hat tool to form apre-cured composite hat stiffener. The pre-cured composite hat stiffenercomprises a composite hat section. The pre-cured composite hat stiffenerfurther comprises a plurality of composite stiffening plies comprising abody ply, a wrap ply, and a base ply, all coupled to the composite hatsection. The pre-cured composite hat stiffener further comprises a pairof radius filler noodles coupled to the composite hat section anddisposed between the plurality of composite stiffening plies. Thepre-cured composite hat stiffener further comprises an outer ply coupledto the composite hat section. The method further comprises bonding thepre-cured composite hat stiffener to an uncured composite pressure webto form a composite hat-stiffened pressure web. The compositehat-stiffened pressure web minimizes a pull-off load at the radiusfiller noodle and improves stability of a pressure web.

The features, functions, and advantages that have been discussed can beachieved independently in various embodiments of the disclosure or maybe combined in yet other embodiments further details of which can beseen with reference to the following description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure can be better understood with reference to the followingdetailed description taken in conjunction with the accompanying drawingswhich illustrate preferred and exemplary embodiments, but which are notnecessarily drawn to scale, wherein:

FIG. 1 is an illustration of a perspective view of an aircraft that mayincorporate one or more exemplary embodiments of a compositehat-stiffened pressure web of the disclosure;

FIG. 2A is an illustration of a front sectional exploded view of one ofthe embodiments of a composite hat stiffener of the disclosure with aslot and in an uncured state;

FIG. 2B is an illustration of the composite hat stiffener of FIG. 2A ina cured state;

FIG. 3A is an illustration of a front cross-sectional view of one of theembodiments of a composite hat stiffener of the disclosure havingchamfered edges;

FIG. 3B is an illustration of a close-up view of the chamfered edge ofcircle 3B shown in FIG. 3A;

FIG. 4A is an illustration of a front sectional exploded view of anotherone of the embodiments of a composite hat stiffener of the disclosurewith no slot and in an uncured state;

FIG. 4B is an illustration of the composite hat stiffener of FIG. 4A ina cured state;

FIG. 5A is an illustration of a front sectional view of one of theembodiments of a composite hat stiffener of the disclosure shown withina tool assembly with a hat tool having a variable tool radius;

FIG. 5B is an illustration of a front sectional view of another one ofthe embodiments of a composite hat stiffener of the disclosure shownwithin a tool assembly with a hat tool having a constant tool radius;

FIG. 6A is an illustration of a perspective view of one of theembodiments of a composite hat-stiffened pressure web of the disclosure;

FIG. 6B is an illustration of an exploded perspective view of thecomposite hat stiffener portion of the composite hat-stiffened pressureweb FIG. 6A;

FIG. 7 is an illustration of a bottom perspective view of an aircrafthorizontal pressure deck with one of the embodiments of a compositehat-stiffened pressure web of the disclosure;

FIG. 8 is an illustration of a back perspective view of a portion of anaircraft aft wheel well bulkhead with another one of the embodiments ofa composite hat-stiffened pressure web of the disclosure; and,

FIG. 9 is a flow diagram of one of the embodiments of a method of thedisclosure.

DETAILED DESCRIPTION

Disclosed embodiments will now be described more fully hereinafter withreference to the accompanying drawings, in which some, but not all ofthe disclosed embodiments are shown. Indeed, several differentembodiments may be provided and should not be construed as limited tothe embodiments set forth herein. Rather, these embodiments are providedso that this disclosure will be thorough and complete and will fullyconvey the scope of the disclosure to those skilled in the art.

Now referring to the Figures, FIG. 1 is an illustration of a perspectiveview of an aircraft 10 that may incorporate one or more exemplaryembodiments of a composite hat-stiffened pressure web 30 (see also FIGS.6A, 7, 8) of the disclosure. As shown in FIG. 1, the aircraft 10comprises a fuselage 12, a nose 14, a cockpit 16, wings 18, one or morepropulsion units 20, a vertical tail portion 22, and horizontal tailportions 24. Although the aircraft 10 shown in FIG. 1 is generallyrepresentative of a commercial passenger aircraft having one or morecomposite hat-stiffened pressure webs 30, the teachings of the disclosedembodiments may be applied to other passenger aircraft, cargo aircraft,military aircraft, rotorcraft, and other types of aircraft or aerialvehicles, as well as aerospace vehicles, satellites, space launchvehicles, rockets, and other aerospace vehicles, as well as boats andother watercraft, trains, automobiles, trucks, buses, or other suitablestructures having one or more composite hat-stiffened pressure webs 30.

In an embodiment of the disclosure, there is provided a composite hatstiffener 32 as shown in FIGS. 2A-2B. FIG. 2A is an illustration of afront sectional exploded view of one of the embodiments of the compositehat stiffener 32, such as in the form of composite hat stiffener 32 a,shown in an uncured state 34, that is, prior to being cured, co-cured,or bonded together. FIG. 2B is an illustration of the composite hatstiffener 32 of FIG. 2A in a cured state 36, that is, after being cured,co-cured, or bonded together.

As shown in FIGS. 2A-2B, the composite hat stiffener 32, such as in theform of composite hat stiffener 32 a, comprises a composite hat section38. As shown in FIG. 2A, the composite hat section 38 has a first side40 and a second side 42. The composite hat section 38 is preferablycomprised of hat section composite plies 43 (see FIG. 2A), such ascarbon fiber reinforced plastic (CFRP) tape, woven fabric, or anothersuitable composite tape, fabric, or fiber reinforced composite material.

As further shown in FIGS. 2A-2B, the composite hat section 38 comprisesa cap 44 having opposite ends 46 from each other. As further shown inFIGS. 2A-2B, the composite hat section 38 further comprises a pair ofwebs 48 or sidewalls extending from the opposite ends 48, respectively,of the cap 44. As further shown in FIGS. 2A-2B, the composite hatsection 38 further comprises a pair of flanges 50. Each flange 50extends outwardly from a base portion 52 (see FIG. 2A) of each web 48,respectively. The pair of flanges 50 are designed to facilitate couplingor mounting of the composite hat stiffener 32 to a structure surface orsubstrate 54 (see FIG. 6A). As further shown in FIGS. 2A-2B, thecomposite hat section 38 comprises a pair of fillet radii 56. The pairof fillet radii 56 couple the pair of flanges 50 to the pair of webs 48,respectively. The pair of fillet radii 56 may add strength and reducestresses at the intersection or fillet of the pair of flanges 50 and thepair of webs 48, and may be beneficial to the tooling or molding processby eliminating sharp corners that may cause cracking or erosion of toolor mold features. As used herein, a “fillet” means a rounded internalcorner, and a “fillet radius” means the radius of the arc that connectsthe filleted components, in this case, the pair of flanges 50 and thepair of webs 48.

Each flange 50 preferably has a chamfered edge 58 (see FIGS. 3A-3B).FIG. 3A is an illustration of a front cross-sectional view of one of theembodiments of the composite hat stiffener 32, such as in the form ofcomposite hat stiffener 32 d, showing the chamfered edge 58 at the endof each flange 50. As used herein, a “chamfered edge” means a flatsurface made by cutting off or removing the edge or corner of a materialor part. FIG. 3A shows the cap 44, the pair of webs 48, the pair offlanges 50, the pair of fillet radii 56, a composite hat stiffener slotopening 106, a pair of radius filler noodles 108 (discussed in detailbelow), and a base center flange 126 of the composite hat stiffener 32,such as in the form of composite hat stiffener 32 d. FIG. 3B is anillustration of a close-up view of the chamfered edge 58 of circle 3Bshown in FIG. 3A. The chamfered edge 58 helps to prevent delamination ofthe composite hat stiffener 32 which may occur during removal of one ormore caul plates 60 (see FIGS. 5A-5B), if such caul plates 60 are used,after curing, co-curing, bonding or co-bonding due to adhesive bleed. Asshown in FIG. 3B, the chamfered edge 58 may comprise a first portion 62having a width 64. The end of the first portion 62 is substantiallyperpendicular to a baseline 66 (see FIG. 3B). As further shown in FIG.3B, the chamfered edge 58 comprises a second angled portion 68 formingan angle 70 to the baseline 66. The angle 70 of the chamfered edge 58may preferably be about 45 degrees or less and greater than zero degreesto the baseline 66 or another suitable size angle. The shallower theangle 70, the better for bondline peeling resistance. The angle 70chosen may depend on producibility tolerances and manufacturing designconstraints for the structure or part being manufactured.

As further shown in FIG. 2A, the composite hat stiffener 32, such as inthe form of composite hat stiffener 32 a, comprises a plurality ofcomposite stiffening plies 72 coupled to the composite hat section 38.The composite stiffening plies 72 may also be coupled to each other. Theplurality of composite stiffening plies 72 preferably comprise aplurality of composite plies 73 (see FIG. 6A), such as carbon fiberreinforced plastic (CFRP) fabric or tape, or another suitable compositewoven fabric, tape, or fiber reinforced composite material.

The hat section composite plies 43 forming the composite hat section 38and the composite plies 73 forming the plurality of composite stiffeningplies 72 may comprise a reinforcement material surrounded by andsupported within a matrix material, such as for example, a prepregmaterial. The reinforcement material may comprise high-strength fibers,such as glass or carbon fibers, graphite, aromatic polyamide fiber,fiberglass, or another suitable reinforcement material. The matrixmaterial may comprise various polymer or resin materials, such as epoxy,polyester, vinyl ester resins, polyetheretherketone polymer (PEEK),polyetherketoneketone polymer (PEKK), bismaleimide, or another suitablematrix material. As used herein, “prepreg” means a woven or braidedfabric or cloth-like tape material, e.g., fiberglass or carbon fibers,that has been impregnated with an uncured or partially cured resin,which is flexible enough to be formed into a desired shape, then“cured,” e.g., by the application of heat in an oven or an autoclave, toharden the resin into a strong, rigid, fiber-reinforced structure. Thehat section composite plies 43 and the composite plies 73 may comprisepreferably comprise carbon fiber reinforced plastic (CFRP) tape or wovenfabric, or another suitable composite tape, fabric, or fiber reinforcedcomposite material.

As further shown in FIGS. 2A-2B, the plurality of composite stiffeningplies 72 comprises a body ply 74. The body ply 74 has a first side 76and a second side 78 (see FIG. 2A). The second side 78 of the body ply74 is coupled, for example, cured, co-cured, or bonded, to the firstside 40 of the composite hat section 38. As shown in FIG. 2B, once thebody ply 74 is coupled, for example, cured, co-cured, or bonded, to thecomposite hat section 38, the body ply 74 is integrated to the flanges50, the webs 48 and the cap 44 of the first side 40 of the composite hatsection 38. As discussed above for the plurality of composite stiffeningplies 72, the body ply 74 preferably comprises a composite woven fabric,such as carbon fiber reinforced plastic (CFRP) fabric, a carbon fiberreinforced plastic (CFRP) tape, or another suitable composite wovenfabric, tape, or fiber reinforced composite material.

As further shown in FIGS. 2A-2B, the plurality of composite stiffeningplies 72 comprises a wrap ply 80. The wrap ply 80 has a first side 82and second side 84 (see FIG. 2A). The second side 84 of the wrap ply 80is substantially coupled, for example, cured, co-cured, or bonded, tofirst portions 86 (see FIG. 2A) of the first side 76 of the body ply 74,and thus, is coupled to the composite hat section 38. Once the wrap ply80 is coupled, for example, cured, co-cured, or bonded, to the compositehat section 38 via the body ply 74, the wrap ply 80 is integrated to thewebs 48 and the cap 44 of the first side 40 of the composite hat section38. As discussed above for the plurality of composite stiffening plies72, the wrap ply 80 preferably comprises a composite woven fabric, suchas carbon fiber reinforced plastic (CFRP) fabric, a carbon fiberreinforced plastic (CFRP) tape, or another suitable composite wovenfabric, tape, or fiber reinforced composite material. The wrap ply 80more preferably comprises a single wrap woven fabric ply. The first side82 of the wrap ply 80 is adjacent a core portion 88 (see FIG. 2A) of thecomposite hat stiffener 32. The wrap ply 80 further has a base portion90 (see FIG. 2A) in which, in one embodiment, a wrap ply slot opening 92(see FIG. 2A) may be formed. In another embodiment, as shown in FIG. 5A,the wrap ply 80 does not have a wrap ply slot opening 92.

As further shown in FIGS. 2A-2B, the plurality of composite stiffeningplies 72 comprises a base ply 94. The base ply 94 has a first side 96and a second side 98. The first side 96 of the base ply 94 issubstantially coupled, for example, cured, co-cured, or bonded, tosecond portions 100 (see FIG. 2A) of the first side 76 of the body ply74, and to portions 102 (see FIG. 2A) of the base portion 90 of the wrapply 80, and thus, is coupled to the composite hat section 38. Once thebase ply 94 is coupled, for example, cured, co-cured, or bonded, to thecomposite hat section 38 via the body ply 74, the base ply 94 isintegrated to the flanges 50 of the first side 40 of the composite hatsection 38. As discussed above for the plurality of composite stiffeningplies 72, the base play 94 preferably comprises a composite wovenfabric, such as carbon fiber reinforced plastic (CFRP) fabric, a carbonfiber reinforced plastic (CFRP) tape, or another suitable compositewoven fabric, tape, or fiber reinforced composite material. The base ply94 more preferably comprises a single cap woven fabric ply.

As shown in FIG. 2A, the base ply 94 may further have, in oneembodiment, a base ply slot opening 104. In another embodiment, as shownin FIG. 5A, the base ply 94 does not have a base ply slot opening 104.As shown in FIG. 2A, prior to when the base ply 94 is coupled, forexample, cured, co-cured, or bonded, to the wrap ply 80, the base plyslot opening 104 and the wrap ply slot opening 92 may be aligned to forma composite hat stiffener slot opening 106 during curing or bonding. Thecomposite hat stiffener slot opening 106 may be used to preventdistortion of the composite hat stiffener 32 during curing or bonding.In addition, when the composite hat stiffener 32 is cured or bonded, theresulting composite hat stiffener slot opening 106 may be small or notof a large enough size as desired. Thus, after curing or bonding of thecomposite hat stiffener 32, the composite hat stiffener slot opening 106may be cut or trimmed further to enlarge or increase the size of thecomposite hat stiffener slot opening 106 in order, for example, toaccommodate nondestructive inspection (NDI) access.

As further shown in FIGS. 2A-2B, the composite hat stiffener 32, such asin the form of composite hat stiffener 32 a, comprises a pair of radiusfiller noodles 108. The pair of radius filler noodles 108 are preferablycoupled to or adjacent to the composite hat section 38 and arepreferably disposed between and intersect the plurality of compositestiffening plies 72 which form radius filler noodle regions 110 (seeFIG. 2A) for the pair of radius filler noodles 108 to be disposedwithin. For purposes of this application, the term “radius filler noodleregion” means the substantially triangular region where the compositehat section 38 and the plurality of composite stiffening plies 72 cometogether or intersect. The radius filler noodles 108 preferably comprisea rolled tape material, such as a rolled composite tape, uni-directionalfibers, epoxy, adhesive, tape and adhesive, laminated tape, closed cellfoam, wood, or another suitable material. Preferably, the composite hatstiffener 32 minimizes a pull-off load at the radius filler noodle 108or minimizes or reduces the effects of pull-off load at the radiusfiller noodle 108, which may result in eliminating or minimizing use ofone or more radius filler elements (not shown), fasteners (not shown),or angle fittings (not shown) to react the pull-off load. In turn, thismay result in increased cost savings due to the elimination orminimization of the cost of the such radius filler elements, fasteners,or angle fittings and elimination or minimization of the labor andmanufacturing costs to install and maintain such radius filler elements,fasteners, or angle fittings.

As further shown in FIGS. 2A-2B, the composite hat stiffener 32, such asin the form of composite hat stiffener 32 a, comprises an outer ply 112.The outer ply 112 has a first side 114 and a second side 116 (see FIG.2A). The first side 114 of the outer ply 112 is coupled, for example,cured, co-cured, bonded, or co-bonded, to the second side 42 of thecomposite hat section 38. Preferably, the outer ply 112 comprises aglass material, such as, for example, a fiberglass material, or anothersuitable glass material. Preferably, the outer ply 112 comprises agalvanic corrosion protection material that protects any adjacent metalstructures or parts, such as adjacent aluminum or steel structures,adjacent the composite hat stiffener 32, against galvanic corrosion. Inaddition, preferably, the outer ply 112 comprises a drill breakoutprotection material that protects against drill breakout or damageduring drilling of the composite hat stiffener 32 or adjacent structuresor parts.

As further shown in FIGS. 2A-2B, the composite hat stiffener 32 maycomprise a peel ply 118. The peel ply 118 has a first side 120 and asecond side 122 (see FIG. 2A). The first side 120 of the peel ply 118may be coupled to the second side 98 of the base ply 94. The peel ply118 may further have a peel ply slot opening 124 (see FIG. 2A). Inanother embodiment, as shown in FIG. 5A, the peel ply 118 does not havea peel ply slot opening 124. Preferably, the peel ply slot opening 124,if present, is also aligned with the base ply slot opening 104 and thewrap ply slot opening 92 to form the composite hat stiffener slotopening 106. As shown in FIG. 2A, prior to when the peel ply 118 iscoupled to the base ply 94, the base ply slot opening 104, the peel plyslot opening 124, and the wrap ply slot opening 92 may be aligned.Preferably, the peel ply 118 comprises a fabric material, such as afiberglass fabric coated with a release agent, coated and uncoated nylonfabrics, or another suitable fabric material. The peel ply 118 may bebonded to the base ply 94, and the peel ply 118 may preferably beremovable and may be peeled off and discarded after use. The peel ply118 may be used to protect the composite hat stiffener 32 from dirt,dust or contaminates that it may be exposed to before being bonded tothe composite hat-stiffened pressure web 30 (see FIG. 6A). Further, Thepeel ply 118 may be used to prepare a bonding surface. The peel ply 118may leave a roughened surface that does not require further preparationbefore curing, laminating, or bonding continues, i.e. sanding/scuffingthe composite hat stiffener 32.

FIG. 4A is an illustration of a front sectional exploded view of anotherone of the embodiments of a composite hat stiffener 32, such as in theform of composite hat stiffener 32 c, with no composite hat stiffenerslot opening 106 (see FIG. 2A) and in an uncured state 34. FIG. 4B is anillustration of the composite hat stiffener 32, such as in the form ofcomposite hat stiffener 32 c, of FIG. 4A in a cured state 36. FIGS.4A-4B show a composite hat section 38. preferably comprised of hatsection composite plies 43 (see FIG. 4A), such as carbon fiberreinforced plastic (CFRP) tape, woven fabric, or another suitablecomposite tape, fabric, or fiber reinforced composite material. FIGS.4A-4B further show the cap 44, the pair of webs 48 or sidewallsextending from opposite ends 48 of the cap 44, respectively, and thepair of flanges 50. FIGS. 4A-4B further show the pair of fillet radii 56which couple the pair of flanges 50 to the pair of webs 48,respectively, the pair of radius filler noodles 108, the core portion88, and the base center flange 126. As shown in FIG. 4A, the compositehat stiffener 32, such as in the form of composite hat stiffener 32 c,further comprises a plurality of composite stiffening plies 72comprising a body ply 74 (see FIGS. 4A-4B), a wrap ply 80 (see FIGS.4A-4B), and the base ply 94 (see FIGS. 4A-4B). FIGS. 4A-4B further showthe outer ply 112 and the peel ply 118.

In another embodiment of the disclosure, as shown in FIG. 6A, there isprovided a composite hat-stiffened pressure web 30. FIG. 6A is anillustration of a perspective view of one of the embodiments of thecomposite hat-stiffened pressure web 30 of the disclosure. As shown inFIG. 6A, the composite hat-stiffened pressure web 30 comprises one ofthe embodiments of the composite hat stiffener 32, as discussed indetail above. The composite hat stiffener 30 is preferably cured and inthe form of a pre-cured composite hat stiffener 33. FIG. 6A shows thepre-cured composite hat stiffener 33 bonded or co-bonded to a structuresurface or substrate 54. Preferably, as shown in FIG. 6A, the structuresurface or substrate 54 is a pressure web 139, such as an uncuredcomposite pressure web 140. Preferably, the surface of the uncuredcomposite pressure web 140 is flat or relatively flat. Thus, in oneembodiment, the composite hat-stiffened pressure web 30 comprises thepre-cured composite hat stiffener 33 bonded or co-bonded to the uncuredcomposite pressure web 140.

FIG. 6B is an illustration of an exploded perspective view of thecomposite hat stiffener 32, in the form of a pre-cured composite hatstiffener 33, of the composite hat-stiffened pressure web 30 of FIG. 6A.As shown in FIG. 6B, the composite hat stiffener 32, in the form of apre-cured composite hat stiffener 33, comprises the composite hatsection 38 (see FIG. 6B), the plurality of composite stiffening plies 72(see FIG. 6B), the outer ply 112 (see FIG. 6B), and the pair of radiusfiller noodles 108 (see FIG. 6A). The composite hat section 38 (see FIG.6B) is discussed in detail above with respect to FIG. 2A, and preferablycomprises the cap 44 (see FIG. 2A), the pair of webs 48 (see FIG. 2A),the pair of flanges 50 (see FIG. 2A), and the pair of fillet radii 56(see FIG. 2A). The composite hat section 38 is preferably comprised ofhat section composite plies 43 (see FIG. 6B), such as made of carbonfiber reinforced plastic (CFRP) tape, woven fabric, or another suitablecomposite tape, fabric, or fiber reinforced composite material.

As further shown in FIG. 6B, the composite stiffening plies 72 comprisethe body ply 74 for coupling adjacent to the composite hat section 38,the wrap ply 80 for coupling adjacent to the body ply 74, and the baseply 94 for coupling adjacent to the body ply 74 and the wrap ply 80. Thesecond side 98 (see FIGS. 6A-6B) of the base ply 94 (see FIG. 6B) isadjacent the structure surface or substrate 54 (see FIG. 6A), such asthe uncured composite pressure web 140 (see FIG. 6A). The plurality ofcomposite stiffening plies 72, including the body ply 74, the wrap ply80, and the base ply 94, preferably comprise a plurality of compositeplies 73 (see FIG. 6B), such as carbon fiber reinforced plastic (CFRP)fabric, carbon fiber reinforced plastic (CFRP) tape, or another suitablecomposite woven fabric, tape, or fiber reinforced composite material.Although FIG. 6B does not show a peel ply 118 (see FIG. 2A), a peel ply118 may be used or applied to the second side 98 of the base ply 94. Thecomposite hat-stiffened pressure web 30 provides the composite hatstiffener 32 bonded to the uncured composite pressure web 140 to provideimproved stability to the uncured composite pressure web 140, ascompared to an existing composite I-beam stiffened pressure web (notshown).

In one embodiment, as shown in FIG. 7, the uncured composite pressureweb 140 may comprise an aircraft horizontal pressure deck pressure web142. FIG. 7 is an illustration of a bottom perspective view of anaircraft horizontal pressure deck 144 with one of the embodiments of thecomposite hat-stiffened pressure web 30, such as in the form ofcomposite hat-stiffened pressure web 30 a. FIG. 7 shows the aircrafthorizontal pressure deck 144 with a keel beam portion 146 and a pressuredeck portion 148. The pressure deck portion 148 includes a pressure web139, such as an uncured composite pressure web 140, preferably in theform of an aircraft horizontal pressure deck pressure web 142.Preferably, the uncured composite pressure web 140, such as in the formof an aircraft horizontal pressure deck pressure web 142, has a flat orrelatively flat surface pressure web or panel. In this embodiment, thecomposite hat-stiffened pressure web 30 a comprises a plurality of thecomposite hat stiffeners 32 a (see also FIGS. 2A, 5A) bonded orco-bonded to the aircraft horizontal pressure deck pressure web 142.Further, in this embodiment, the pair of radius filler noodles 108 ofthe composite hat stiffeners 32 a bonded or co-bonded to the aircrafthorizontal pressure deck pressure web 142 each comprises a variablenoodle radius 150 (see also FIG. 5A).

In another embodiment, as shown in FIG. 8, the pressure web 139, such asthe uncured composite pressure web 140, may comprise an aircraft aftwheel well bulkhead pressure web 152. FIG. 8 is an illustration of aback perspective view of a portion of an aircraft aft wheel wellbulkhead 154 with another one of the embodiments of the compositehat-stiffened pressure web 30, such as in the form of compositehat-stiffened pressure web 30 b. FIG. 8 shows a portion of the aircraftaft wheel well bulkhead 154 with the uncured composite pressure web 140,in the form of the aircraft aft wheel well bulkhead pressure web 152.Preferably, the uncured composite pressure web 140, such as in the formof the aircraft aft wheel well bulkhead pressure web 152, has a flat orrelatively flat surface pressure web or panel. In this embodiment, thecomposite hat-stiffened pressure web 30 b comprises a plurality of thecomposite hat stiffeners 32 b (see also FIG. 5B) bonded or co-bonded tothe aircraft aft wheel well bulkhead pressure web 152. Further, in thisembodiment, the pair of radius filler noodles 108 of the composite hatstiffeners 32 b bonded or co-bonded to the aircraft aft wheel wellbulkhead pressure web 152 each comprises a constant noodle radius 156(see also FIG. 5B).

In another embodiment of the disclosure, there is provided a method 200(see FIG. 9) of making a composite hat-stiffened pressure web 30 (seeFIG. 6A) to reduce or minimize the effects of pull-off load at theplurality of radius filler noodles 108 or the radius filler noodle 108(see FIG. 2A), to reduce criticality to pull-off load at the pluralityof radius filler noodles 108 or the radius filler noodle 108 (see FIG.2A) or by the composite hat-stiffened pressure web 30, and to improvestability of a pressure web 139 (see FIGS. 6A, 7, 8), such as an uncuredcomposite pressure web 140 (see FIG. 6A). FIG. 9 is a flow diagram ofone of the embodiments of the method 200 of the disclosure. Inparticular, novel configurations of pressure webs 139 are provided tomake wheel well panels, such as aft wheel well panels, including for theaircraft aft wheel well bulkhead 154 (see FIG. 8), and panels for theaircraft horizontal pressure deck 144 (see FIG. 7).

The method 200 comprises step 202 of curing a composite hat stiffener32, such as for example, a composite hat stiffener 32 a (see FIG. 5A) ora composite hat stiffener 32 b (see FIG. 5B) in a hat tool 130 (seeFIGS. 5A-5B) to form a pre-cured composite hat stiffener 33 (see FIG.6A). The pre-cured composite hat stiffener 33 comprises a composite hatsection 38 (see FIG. 6B). The pre-cured composite hat stiffener 33further comprises a plurality of composite stiffening plies 72 (see FIG.6B) comprising a body ply 74 (see FIG. 6B), a wrap ply 80 (see FIG. 6B),and a base ply 94 (see FIG. 6B), all coupled to the composite hatsection 38 (see FIG. 6B). The pre-cured composite hat stiffener 33further comprises a pair of radius filler noodles 108 (see FIG. 6A)coupled to the composite hat section 38 and disposed between theplurality of composite stiffening plies 72. The pre-cured composite hatstiffener 33 further comprises an outer ply 112 (see FIG. 6B) coupled tothe composite hat section 38.

FIG. 5A is an illustration of a front sectional view of one of theembodiments of a composite hat stiffener 32, such as in the form ofcomposite hat stiffener 32 a, shown within a tool or mold assembly 128.As shown in FIG. 5A, the tool or mold assembly 128 comprises a hat toolor mold 130, such as a female hat tool or mold 132.

Prior to curing, the composite hat stiffener 32, such as in the form ofcomposite hat stiffener 32 a, may be formed by laying up the hat sectioncomposite plies 43 (see FIG. 6B) of the composite hat section 38 (seeFIG. 6B), the composite plies 73 (see FIG. 6B) of the plurality ofcomposite stiffening plies 72 (see FIG. 6B), and the outer ply 112 (seeFIG. 6B) on the surface of the hat tool or mold 130 (see FIG. 5A). Thehat section composite plies 43, the composite plies 73, and the outerply 112 may be laid up by hand on the hat tool or mold 130. The pair ofradius filler noodles 108 are preferably rolled, formed and insertedinto the uncured composite hat stiffener 32 a in the hat tool or mold130. Alternatively, the hat section composite plies 43, the compositeplies 73, and the outer ply 112 may be laid up on a tooling surface (notshown) such as a flat tooling surface by hand or through use of anautomatic tape lay-up machine and then pressed into the hat tool or mold130, such as by a process utilizing hot drape forming or another knownforming process, in order to form the hat section composite plies 43,the composite plies 73, the outer ply 112, and the pair of radius fillernoodles 108 into the shape of the composite hat stiffener 32.Alternatively, other suitable known lay-up or forming processes may beused. Prior to curing, a mandrel (not shown) may be inserted in the coreportion 88 (see FIG. 2A) of the composite hat stiffener 32, such as inthe form of hat stiffener 32 a, for winding the plies over or around themandrel, and then the mandrel may be removed after curing. The mandrelmay comprise soft tooling or hard tooling known in the art.

As shown in FIG. 5A, the tool or mold assembly 128 preferably furthercomprises a caul plate 60. The caul plate 60 is preferably of a similarsize and shape to the size and shape of the composite hat stiffener 32.The caul plate 60 is preferably placed in contact with the composite hatstiffener 32 during curing to transmit pressure, to assist in forcingthe composite material into the variable tool radius 135 and to smoothout any irregularities and provide a smooth surface.

As shown in FIG. 5A, the tool or mold assembly 128 preferably furthercomprises a bladder element 134. The bladder element 134 is preferablyinflatable in order to exert pressure from the interior of the hat toolor mold 130 against the composite hat stiffener 32 during curing. Thebladder element 134 preferably has a constant bladder cross-section 138.Because the bladder element 134 has a constant bladder cross-section 138and the radius of the bladder element 134 preferably does not change, itis important to control the radius of the hat tool or mold 130 thatcontacts the exterior of the composite hat stiffener 32. In oneembodiment, where the composite hat stiffener 32, such as in the form ofcomposite hat stiffener 32 a, is cured to form a pre-cured composite hatstiffener 33 and is bonded or co-bonded to the uncured compositepressure web 140, such as in the form of the aircraft horizontalpressure deck pressure web 142 (see FIG. 7), the hat tool or mold 130preferably has a variable tool radius 135 (see FIG. 5A) and the pair ofradius filler noodles 108 each have a variable noodle radius 150 (seeFIG. 5A). The pre-cured composite hat stiffener 33 that is bonded to theuncured composite pressure web 140, such as in the form of the aircrafthorizontal pressure deck pressure web 142 (see FIG. 7), has ply dropsand thus has a variable noodle radius 150. As used herein, “ply drops”means a series of shortened or terminated individual plies or groups ofplies introduced at various locations within the composite part orlamination accomplished by thickness tapering from a thick cross-sectionto a thinner cross-section, for example, to create a composite parthaving a desired surface contour or shape. The ply drops are preferablymachined into the bond assembly jig (BAJ) surfaces of the hat tool ormold to which the uncured composite pressure web 140 is laid up on ancured to allow for a bonding surface, preferably a flat or relativelyflat bonding surface, between the pre-cured composite hat stiffener 33and the uncured composite pressure web 140, such as in the form of theaircraft horizontal pressure deck pressure web 142. The pair of radiusfiller noodles 108 of the pre-cured composite hat stiffener 33 bonded tothe aircraft horizontal pressure deck pressure web 142 may have a noodleoverfill ratio, which means that due to the material of the radiusfiller noodle 108 shrinking during curing, the radius filler noodle 108may be overfilled or made larger than the noodle region it fits into,for example, a noodle overfill ratio of 100%.

FIG. 5B is an illustration of a front sectional view of another one ofthe embodiments of a composite hat stiffener 32, such as in the form ofcomposite hat stiffener 32 b, shown within the mold or tool assembly128. As shown in FIG. 5B, the tool or mold assembly 128 comprises a hattool or mold 130, such as a female hat tool or mold 132, a caul plate 60as discussed above, and a bladder element 134 as discussed above. Thebladder element 134 preferably has a constant bladder cross-section 138.In another embodiment, where the composite hat stiffener 32, such as inthe form of composite hat stiffener 32 b, is cured to form a pre-curedcomposite hat stiffener 33 and is bonded or co-bonded to the uncuredcomposite pressure web 140, such as in the form of the aircraft aftwheel well bulkhead pressure web 152 (see FIG. 8), the hat tool or mold130 preferably has a constant tool radius 136 (see FIG. 5B) and the pairof radius filler noodles 108 each preferably have a constant noodleradius 156 (see FIG. 5B). In both the aircraft horizontal pressure deckpressure web 142 and the aircraft aft wheel well bulkhead pressure web152, the part radius adjacent to the variable noodle radius 150 isconstant. In the aircraft aft wheel well bulkhead pressure web 152, theradii are constant. In the aircraft horizontal pressure deck pressureweb 142, the variable tool radius 135 is variable. The pre-curedcomposite hat stiffener 33 that is bonded to the uncured compositepressure web 140, such as in the form of the aircraft aft wheel wellbulkhead pressure web 152 (see FIG. 8), has no ply drops and thus has aconstant noodle radius 156. Although there are no ply drops with thisembodiment, ply drops are preferably still machined into the surfaces ofthe uncured composite pressure web 140 to allow for a bonding surface,preferably a flat or relatively flat bonding surface, between thepre-cured composite hat stiffener 33 and the uncured composite pressureweb 140, such as in the form of the aircraft aft wheel well bulkheadpressure web 152. The pair of radius filler noodles 108 of the pre-curedcomposite hat stiffener 33 bonded to the aircraft aft wheel wellbulkhead pressure web 152 may have a noodle overfill ratio of 115%,which means that due to the material of the radius filler noodle 108shrinking during curing, the radius filler noodle 108 may be overfilledor made larger than the noodle region it fits into, for example, anoodle overfill ratio of 115%.

The curing step 202 may comprise a known curing process such as anautoclave curing process, a vacuum bag curing process, a combinationautoclave and vacuum bagging curing process, a compression mold curingprocess, a resin transfer molding process, a room temperature curingprocess, or another suitable curing process. The curing may take placeat an elevated temperature and pressure as required per materialspecifications to effectively cure the composite hat stiffener 32.During curing, the composite material of the composite hat stiffener 32hardens and holds the shape of the hat tool or mold 130. Once thepre-cured composite hat stiffener 33 is formed, the pre-cured compositehat stiffener 33 may be removed from the hat tool or mold 130.

As further shown in FIG. 9, the method 200 further comprises step 204 ofbonding or co-bonding the pre-cured composite hat stiffener 33 (see FIG.6A) to a structure surface or substrate 54 (see FIG. 6A), preferably ina pressure web 139, such as an uncured composite pressure web 140 (seeFIG. 6A), to form a composite hat-stiffened pressure web 30 (see FIG.6A). The pre-cured composite hat stiffener 33 may be bonded or co-bondedto the uncured composite pressure web 140 via adhesive bonding,co-curing, secondary bonding, or another known bonding or co-bondingprocess. The bonding step 204 may take place at an elevated temperatureand pressure as required per material specifications to effectively bondor co-bond the pre-cured composite hat stiffener 33 (see FIG. 6A) to theuncured composite pressure web 140.

The composite hat-stiffened pressure web 30 preferably minimizes apull-off load at the plurality of radius noodle fillers 108 or at theradius noodle filler 108 and improves stability of the pressure web 139(see FIG. 6A). The pre-cured composite hat stiffener 33 bonded orco-bonded to the uncured composite pressure web 140 provides improvedstability and buckling resistance to the uncured composite pressure web140, as compared to existing and known composite I-beam stiffenedcomposite pressure web or skin panels (not shown).

As further shown in FIG. 9, the method 200 may comprise prior to step202 of curing the composite hat stiffener 32, an optional step 206 ofcoupling a peel ply 118 to the composite hat stiffener 32, and aftercuring, removing the peel ply 118 from the composite hat stiffener 32.As further shown in FIG. 9, the method 200 may comprise prior to step202 of curing the composite hat stiffener 32, an optional step 208 ofadding a composite hat stiffener slot opening 106 to the composite hatstiffener 32, and after curing, optionally enlarging the composite hatstiffener slot opening 106, as discussed above. As further shown in FIG.9, the method 200 may comprise prior to step 202 of curing the compositehat stiffener 32, an optional step 210 of chamfering edges of a pair offlanges 50 (see FIGS. 3A-3B) of the composite hat stiffener 32.

As further shown in FIG. 9, the step 204 of bonding of the method 200may further comprise an optional step 212 of bonding the pre-curedcomposite hat stiffener 33 to an aircraft wheel well bulkhead pressureweb 152 (see FIG. 8). As further shown in FIG. 9, the method 200 maycomprise prior to step 202 of curing the composite hat stiffener 32,optional step 214 of controlling a variable tool radius 135 (see FIG.5A) and a variable noodle radius 150 (see FIG. 5A), and wherein the step204 of bonding further comprises bonding the pre-cured composite hatstiffener 33 to an aircraft horizontal pressure deck pressure web 142(see FIG. 7).

As will be appreciated by those of skill in the art, incorporating thenovel composite hat-stiffened pressure web 30 of the disclosure into,e.g., the wheel well panels of a composite bodied aircraft, for example,into the aircraft horizontal pressure deck 144 (see FIG. 7) and/or theaircraft aft wheel well bulkhead 154 (see FIG. 8), results in a numberof substantial benefits. Disclosed embodiments of the composite hatstiffener 32 (see FIGS. 2A-5B), the composite hat-stiffened pressure web30, and method 200 (see FIG. 9) provide a unique design that uses apre-cured composite hat stiffener 33 (see FIG. 6A), comprised of acomposite tape composite hat section 38 with a plurality of compositestiffening plies 72 made of composite woven fabric plies applied on allthree charges at the charge interface of the composite hat section 38,where the pre-cured composite hat stiffener 33 is bonded or co-bonded toan uncured composite pressure web 140 (see FIG. 6A) such as made ofcomposite tape. Further, disclosed embodiments of the composite hatstiffener 32 (see FIGS. 2A-5B), the composite hat-stiffened pressure web30, and method 200 (see FIG. 9) provide a design that improvesstability, strength, and buckling resistance of the uncured compositepressure web 140, such as in the form of an aircraft horizontal pressuredeck pressure web 142 and an aircraft wheel well bulkhead pressure web152. Such design provides improved stability for the uncured compositepressure web 140, as compared to an existing or known compositeI-stiffened pressure web (not shown), and minimizes a pull-off load atthe radius filler noodle of existing composite I-stiffener beams orpanels, thus eliminating the need for radius filler elements, fasteners,or angle fittings typically used to prevent a failure and to accommodatepull-off loading concerns. Moreover, disclosed embodiments of thecomposite hat stiffener 32 (see FIGS. 2A-5B) and the compositehat-stiffened pressure web 30 have a different critical detail forpull-off load, thus improving their ability to handle pull-off inducedloads. Because disclosed embodiments of the composite hat stiffener 32(see FIGS. 2A-5B), the composite hat-stiffened pressure web 30, andmethod 200 (see FIG. 9) may minimize a pull-off load at the radiusfiller noodle, such as at the pair of radius filler noodles 108, whichmay result in eliminating or minimizing use of one or more radius fillerelements, fasteners, or angle fittings to react the pull-off load, thismay result in increased cost savings due to the elimination orminimization of the cost of using such radius filler elements,fasteners, or angle fittings and the elimination or minimization oflabor and manufacturing costs to install and maintain such radius fillerelements, fasteners, or angle fittings.

Many modifications and other embodiments of the disclosure will come tomind to one skilled in the art to which this disclosure pertains havingthe benefit of the teachings presented in the foregoing descriptions andthe associated drawings. The embodiments described herein are meant tobe illustrative and are not intended to be limiting or exhaustive.Although specific terms are employed herein, they are used in a genericand descriptive sense only and not for purposes of limitation.

What is claimed is:
 1. A method of making a composite hat stiffener, themethod comprising the steps of: adding a composite hat stiffener slotopening to the composite hat stiffener; curing the composite hatstiffener in a hat tool to form a pre-cured composite hat stiffener, thepre-cured composite hat stiffener comprising: a composite hat section; aplurality of composite stiffening plies comprising a body ply, a wrapply, and a base ply, all coupled to the composite hat section, whereinthe body ply is coupled to a first side of the composite hat section,the wrap ply is coupled to the body ply, and the base ply is coupled tothe body ply and the wrap ply; a vacant composite hat stiffener slotopening positioned at a base portion of the composite hat stiffener andformed by alignment of a wrap ply slot opening and a base ply slotopening; a pair of radius filler noodles coupled to the composite hatsection and disposed between the plurality of composite stiffeningplies; and, an outer ply coupled to the composite hat section; and,bonding the pre-cured composite hat stiffener to a structure surface. 2.The method of claim 1 further comprising prior to the step of curing thecomposite hat stiffener, the step of coupling a peel ply to thecomposite hat stiffener, and after the step of curing, the step ofremoving the peel ply from the composite hat stiffener.
 3. The method ofclaim 1 further comprising after the step of curing, optionally the stepof enlarging the composite hat stiffener slot opening.
 4. The method ofclaim 1 further comprising prior to the step of curing the composite hatstiffener, the step of chamfering edges of a pair of flanges of thecomposite hat stiffener.
 5. The method of claim 1 wherein the step ofbonding further comprises the step of bonding the pre-cured compositehat stiffener to an aircraft wheel well bulkhead pressure web.
 6. Themethod of claim 1 further comprising prior to the step of curing thecomposite hat stiffener, the step of controlling a variable tool radiusand a variable noodle radius, and wherein the step of bonding furthercomprises bonding the pre-cured composite hat stiffener to an aircrafthorizontal pressure deck pressure web.
 7. The method of claim 1 whereinthe step of curing the composite hat stiffener to form the pre-curedcomposite hat stiffener further comprises curing the composite hatstiffener to form the pre-cured composite hat stiffener comprising: acap; a pair of webs extending from opposite ends of the cap, a pair offlanges; and, a pair of fillet radii coupling the pair of flanges to thepair of webs, respectively.
 8. The method of claim 1 wherein the step ofcuring the composite hat stiffener to form the pre-cured composite hatstiffener further comprises forming the composite hat section comprisinga plurality of hat section composite plies comprised of a carbon fiberreinforced plastic (CFRP) tape.
 9. The method of claim 1 wherein thestep of curing the composite hat stiffener to form the pre-curedcomposite hat stiffener further comprises forming the composite hatsection comprising a plurality of hat section composite plies comprisedof a carbon fiber reinforced plastic (CFRP) fabric.
 10. The method ofclaim 1 wherein the step of curing the composite hat stiffener to formthe pre-cured composite hat stiffener further comprises forming theouter ply comprising a glass material.
 11. The method of claim 1 whereinthe step of curing the composite hat stiffener to form the pre-curedcomposite hat stiffener further comprises forming the outer plycomprising a galvanic corrosion protection material and a drill breakoutprotection material.
 12. A method of making a composite hat stiffener,the method comprising the steps of: curing a composite hat stiffener ina hat tool to form a pre-cured composite hat stiffener, the pre-curedcomposite hat stiffener comprising: a composite hat section having afirst side and a second side; a plurality of composite stiffening pliescoupled to the composite hat section, the plurality of compositestiffening plies comprising: a body ply coupled to the first side of thecomposite hat section; a wrap ply coupled to the body ply, the wrap plyhaving a wrap ply slot opening formed in a base portion of the wrap ply;and, a base ply coupled to the body ply and the wrap ply, the base plyhaving a base ply slot opening; a vacant composite hat stiffener slotopening positioned at a base portion of the composite hat stiffener andformed by alignment of the wrap ply slot opening and the base ply slotopening; a pair of radius filler noodles coupled to the composite hatsection and disposed between the plurality of composite stiffeningplies; and, an outer ply coupled to the second side of the composite hatsection, the outer ply comprising a glass material and a galvaniccorrosion protection material; bonding the pre-cured composite hatstiffener to a structure surface.
 13. The method of claim 12 furthercomprising prior to the step of curing the composite hat stiffener, thestep of coupling a peel ply to the composite hat stiffener, and afterthe step of curing, the step of removing the peel ply from the compositehat stiffener.
 14. The method of claim 12 further comprising prior tothe step of curing the composite hat stiffener, the step of chamferingedges of a pair of flanges of the composite hat stiffener.
 15. Themethod of claim 12 wherein the step of bonding further comprises thestep of bonding the pre-cured composite hat stiffener to an aircraftwheel well bulkhead pressure web.
 16. The method of claim 12 wherein thestep of curing the composite hat stiffener to form the pre-curedcomposite hat stiffener further comprises curing the composite hatstiffener to form the pre-cured composite hat stiffener comprising: acap; a pair of webs extending from opposite ends of the cap, a pair offlanges; and, a pair of fillet radii coupling the pair of flanges to thepair of webs, respectively.
 17. A method of making a compositehat-stiffened pressure web to reduce effects of a pull-off load and toimprove stability of a pressure web, the method comprising the steps of:adding a composite hat stiffener slot opening to the composite hatstiffener; curing the composite hat stiffener in a hat tool to form apre-cured composite hat stiffener, the pre-cured composite hat stiffenercomprising: a composite hat section; a plurality of composite stiffeningplies comprising a body ply, a wrap ply, and a base ply, all coupled tothe composite hat section; a vacant composite hat stiffener slot openingpositioned at a base portion of the composite hat stiffener and formedby alignment of a wrap ply slot opening and a base ply slot opening; apair of radius filler noodles coupled to the composite hat section anddisposed between the plurality of composite stiffening plies; and, anouter ply coupled to the composite hat section; and, bonding thepre-cured composite hat stiffener to an uncured composite pressure webto form a composite hat-stiffened pressure web, wherein the compositehat-stiffened pressure web minimizes a pull-off load at the radiusfiller noodle and improves stability of a pressure web.
 18. The methodof claim 17 further comprising prior to the step of curing the compositehat stiffener, the step of coupling a peel ply to the composite hatstiffener, and after the step of curing, the step of removing the peelply from the composite hat stiffener.
 19. The method of claim 17 furthercomprising after the step of curing optionally the step of enlarging thecomposite hat stiffener slot opening.
 20. The method of claim 17 furthercomprising prior to the step of curing the composite hat stiffener, thestep of chamfering edges of a pair of flanges of the composite hatstiffener.